Area Forecast Discussion
Issued by NWS Greer, SC

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FXUS62 KGSP 171802

Area Forecast Discussion
National Weather Service Greenville-Spartanburg SC
102 PM EST Wed Jan 17 2018

A cold front will move southeast of the area later this morning with
snow likely across the forecast area. In the wake of the front, high
pressure will overspread the region later this evening and tomorrow
and drift offshore by early Saturday. Another cold front is expected
to approach the Carolinas early next week.


As of 1250 pm: Latest water vapor imagery indicates dry slot moving
quickly east across the Piedmont this afternoon, and as such, the
back edge of the snow is speeding up while radar imagery indicates
quickly diminishing snowfall rates along the back edge of the precip
shield. Therefore, this things going to come to an end pretty
quickly here over the next 1-3 hours. For safe-keeping, part of the
Winter Storm Warning and Advisory that was set to expire at noon was
extended til 3pm. It will probably be replaced with an Advisory for
black ice before then, with details regarding other areas that will
need a "Black Ice Advisory" still to be hashed out. Otherwise, areas
along the I-77 corridor could see another inch or perhaps 2 before
the snow ends during late afternoon/early evening.

Temps will be well below normal through tonight. Gusty winds and
temps in the single digits and teens will result in continued wind
chill issues over the mtns, especially the high terrain. Wind Chill
Advisory remains in effect overnight and into Thursday morning. The
tonight period should be mostly clear and cold with fresh snow
across parts of the area.


As of 230 AM EST Wednesday: The short term looks very quiet, as dry
quasi-zonal flow sets up across the eastern states. Dry sfc high
pres will settle in across the Deep South Thursday, lingering thru
Friday. Temps will start out cold Thursday morning, rebounding into
the 30s to mid 40s in the aftn under full sunshine. Melting snow may
limit max temps a category or so, but still expect good melting.
Whatever roads are wet will refreeze Thursday night, with temps
dipping into the upper teens to mid 20s. A warming trend will ensue
for Friday, with temps warming to near normal, mainly upper 40s
mountains and lower to mid 50s piedmont under sunny skies. Lows
Friday night under clear skies and light winds will be in the 20s.


As of 305 AM EST Wednesday: the extended forecast begins at 12z on
Saturday with broad upper ridging in place over the eastern 2/3 of
the CONUS and a deep upper trof over the West Coast. Over the next
12 to 24 hrs, the long-range models try to develop a closed upper
low over the far southeast and move it offshore by late Sunday.
On Monday, the previously mentioned West Coast trof will approach
the fcst area and likely take on a more negative tilt as it moves
over the area on Tuesday. At the sfc, dry high pressure will be
centered just off the SE Coast with low-lvl flow out of the SW.
As we move into Sunday, the high will slide farther offshore while
a low pressure system deepens over the Great Plains. The low is
expected to track NE towards the Great Lakes and bring a strong
cold front to our doorstep on Monday. Most of the model guidance
has the front east of the CWFA by early Tues with another round
of dry high pressure in its wake. As for the sensible fcst, no
major changes were needed with PoPs ramping up late Sunday and
into Monday. By early Tues, most of the precip is expected to be
east of the CWFA, however I did keep a chance for some light NW
flow snow showers over the NC/Tenn border region.


At KCLT/KHKY Although the back edge of the snow is still about 3-4 hours
away, drier mid-level air working in from the southwest is resulting
in diminishing snowfall rates across eastern portions of Upstate SC.
Therefore, the window for visby < 1SM is closing, and the tempo for
such has been shortened to end at 19Z, with visby expected to
improve to 5SM by 20Z. MVFR/low VFR conditions should develop no
later than 22Z, with clearing skies expected this evening, and SKC
conditions continuing through the period. Very cold temperatures
tonight will result in any melt water refreezing. Winds will remain
N/NE to N/NW at around 10 kts through the period.

Elsewhere: May still see some flurries at the Upstate SC terminals
and KAVL through late afternoon. Otherwise, MVFR/low VFR cigs should
lift to VFR by late this afternoon, with clearing skies this
evening, and SKC conditions continuing through the period. Very cold
temperatures tonight will result in any melt water refreezing. Winds
will remain N/NE to N/NW at around 10 kts through the period, with
gusts of 20-25 kts expected to continue at KAVL until at least Thu

Outlook: Dry/VFR condition are expected to continue through the
week and into the weekend.

Confidence Table...

            18-24Z        00-06Z        06-12Z        12-18Z
KCLT       Med   68%     High 100%     High 100%     High 100%
KGSP       High  82%     High 100%     High 100%     High 100%
KAVL       High  96%     High 100%     High 100%     High 100%
KHKY       High  85%     High 100%     High 100%     High 100%
KGMU       Med   77%     High 100%     High 100%     High 100%
KAND       High  98%     High 100%     High 100%     High 100%

The percentage reflects the number of guidance members agreeing
with the scheduled TAF issuance flight rule category. Complete hourly
experimental aviation forecast consistency tables and ensemble forecasts
are available at the following link:


NC...Winter Storm Warning until 3 PM EST this afternoon for NCZ068-
     Wind Chill Advisory until 7 AM EST Thursday for NCZ048-051>053-
     Wind Chill Advisory until 10 AM EST Thursday for NCZ033-049-
     Winter Storm Warning until 6 PM EST this evening for
SC...Winter Storm Warning until 3 PM EST this afternoon for
     Winter Storm Warning until 6 PM EST this evening for SCZ009-
     Winter Weather Advisory until 3 PM EST this afternoon for


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